1. Field of the Invention
The present invention relates to an optimal direction-based flooding method for mobile ad-hoc networks, and more particularly, to an optimal direction-based flooding method for effectively relaying a broadcast message for mobile ad-hoc networks.
2. Discussion of the Related Art
Recently, as network terminals have become smaller, a user's need for connecting to a network while on the move has increased, an age in which the computing resource of the terminal itself can sufficiently perform a router roll, has arrived, and technologies for connecting near network terminals with each other are thus needed.
An ad-hoc network was developed for military and rescue purposes, but now the ad-hoc network is being researched in various fields for commercial utilization. An ad-hoc network is an aggregation of wireless mobile hosts constructing a temporary network (Ad-hoc) without center-concentrated management or a standardized support service.
A mobile ad-hoc network represents a network for a radio communication area constructed by mobile terminals without a wired infrastructure network, and is able to construct an emergency rescue network in mountainous or war areas without a wired infrastructure base. Then, current data link technology is utilized to transmit and receive radio signals, and a mobile terminal of the mobile ad-hoc network functions as a host and a router. Herein, the development of router protocol, and technology for security problems of radio signals are needed.
More precisely, a mobile ad-hoc network is a self-built up network of ad-hoc nodes in an infrastructure-less environment, it needs no basic network device such as a base station, and the ad-hoc network needs peer-to-peer (P2P) communication among the ad-hoc nodes using a radio channels. Since a network topology of a mobile ad-hoc network can be varied due to the mobility of the ad-hoc nodes, the complexity of the network can be increased, but research of mobile ad-hoc networks is in progress because of the advantage of replacing the wired network with wireless technology.
The network topology varies more frequently in the mobile ad-hoc network than in a wired network because of the mobility of the nodes and the deficiency of batteries, and a broadcasting method is generally used for solving the problem in the routing and service protocol in the mobile ad-hoc network.
The prior art for decreasing the quantity of the broadcast messages in the broadcasting method are classified into probability-based, counter-based, topology-based, and position-based methods according to the information used.
The probability-based method is a method for determining whether to transmit the broadcast message probabilistically at the node which received the broadcast message. The counter-based method is a method for determining whether to transmit the broadcast message according to a number of repeatedly-received messages. The position-based method is a method for selecting, at a transmitting node, a relay node set by using coordinate information and distance between neighbor nodes, and for determining a transmitting sequence. The topology-based method is a method for exchanging topology information among nodes and selecting a relay node set using the topology information.
As to the prior art, US Patent application No. 20020145978A1 (filed in Oct. 10, 2002) entitled “MRP-Based Hybrid Routing For Mobile Ad Hoc Network” discloses an effective routing method in a mobile ad-hoc network.
The above-noted patent discloses contents by which duplicated re-relaying of the broadcast message and inefficient consumption of radio resources can be reduced by using information of 2-hop neighbor nodes and selecting a next relay node set in a network in which an overhead caused by periodic hello message exchanging can be reduced.
A simple broadcasting method is a flooding method.
The flooding method is a packet relaying method for broadcasting packets to a whole network. Because a routing protocol, a service searching protocol, and an address automatic set-up protocol essentially use the flooding method in a mobile ad-hoc network, the efficiency of the flooding method is an important element for determining the capability of the mobile ad-hoc network. Particularly, since every node in the ad-hoc network uses a shared radio channel and has the characteristic that wireless transmitting areas among neighbor nodes are superimposed, contention for the radio resources, packet collision, and degradation of network capability by duplication of the broadcast packet are considered as big problems.
The conventional flooding method has many problems in a mobile ad-hoc network which has nodes with limited resources because the conventional flooding method causes frequent broadcasting. More particularly, broadcasting by the conventional flooding method has duplicated message relaying and increases the occurrence of contention and collision among nodes using common media. Therefore, inefficient energy consumption and delays in transmitting the broadcast message occur, which are generally called broadcast storm problems.